Decanted phosphate: effects on soil fertility and production of Marandu grass depending on soil acidity

Abstract

Decanted phosphate (DP) is a by-product of wastewater treatment with phosphoric acid (H3PO4), used as phosphate fertilizer in pastures. This experiment was conducted in a greenhouse using a sandy clay loam Typic Haplustox to evaluate the potential effects of DP on soil fertility, and production and nutrition of the Marandu grass during three growths periods in the presence or absence of lime. The experiment was conducted in a completely randomized experimental design with three replications in a 6 × 2 × 2 factorial arrangement: six doses of phosphorus (P), two sources of P, and presence (P/L) or absence (A/L) of lime. We used 0, 30, 60, 90, 120, and 150 mg kg-1 of P, applied as DP or triple superphosphate (TS). Lime was applied to the soil to raise the base saturation to 60%. The DP can be recommended for fertilization in pastures because of its residual supply of P to plants and its ability to decrease the soil acidity and increase the calcium (Ca) content in soil and uptake by plants. The supply of P to the soil by DP is higher under low soil acidity. The use of DP did not alter the contents of zinc (Zn), manganese (Mn), and copper (Cu) in shoots of the Marandu grass.